1. Field of the Invention
The present invention relates to hoisting devices and especially to a cable guide keeping a cable stretched between the derrick itself and the hoisting accessories being supported by the crane by means of cords so as not to be effected and dislocated, especially by gusts.
2. Description of the Prior Art
In lifting load carrying bins, such as containers, special hoisting accessories are used, e.g. a derrick, bridle, supported by hoisting cables from a derrick or the like, is equipped with gripping elements to grip a container and during movement to retain it to the derrick bridle. The derrick bridle generally being adjustable to different container sizes has gripping elements for retaining the containers, the elements being equipped with electromechanic and/or hydraulic components. Independent of the type of guiding devices being used a supply line for current to the derrick itself is necessary and so are lines for transmitting signals from different sensors of the derrick bridle to the operator cabin giving the derrick operator the possibility of informing himself of the operation position of the bridle.
Although the invention is described in connection with a derrick bridle, as known to those skilled in the art, it can be adapted to many different types of hoisting devices.
The derrick bridle and its load is very heavy and will not be especially affected by winds. So is the case with the cable which is generally stretched between the derrick or the like and the derrick bridle over a distance of up to 30 to 40 m. The cable comprising a variety of different conductors, however, has a comparatively large diameter and so catches a great deal of wind. There does not need to be a particularly strong wind to affect the cable being and to push it sidewise out of the vertical of its normal position since such cable has comparatively little weight. This means that derricks today often are forced to stop operation at rather moderate wind forces not because the wind affects the load per se, but because the risk is rather large that such a cable might be pushed aside by the wind and hook on other objects or by other means be affected by stresses causing it to break or to damage objects.
There have been many different attempts to solve the problem of a cable being affected by winds. For example, it has been tried to increase the weight of the cable by attaching chains to it and to keep it stretched by means of various windlasses. None of these attempts have, however, been successful, the cable in these cases being strained at its sockets and being exposed to rupture. The application of windlasses is a very expensive procedure for keeping such heavy elements as cables stretched.
The present invention aims to overcome these problems mentioned above. The problem is solved with an arrangement according to the claims characterizing the invention.